Carbon nanotubes are hexagonal networks of carbon atoms forming seamless tubes with each end capped with half of a fullerene molecule. They were first reported in 1991 by Sumio Iijima who produced multi-layer concentric tubes or multi-walled carbon nanotubes by evaporating carbon in an arc discharge. Carbon nanotubes (CNTs) possess certain electronic and mechanical properties, making them candidates for applications relating to composite materials, nanoelectronics, sensors, and electron field emitters. CNTs can be utilized individually or as an ensemble to build a variety of devices. For instance, individual nanotubes have been used as tips for scanning probe microscopy and as mechanical nano-tweezers. Ensembles of nanotubes have been used for field emission based flat-panel displays, and it has been suggested that bulk quantities of nanotubes may be used as a high-capacity hydrogen storage media. The electronic behavior of CNTs is closely related to their structure, i.e., tip curvature, radius and composition, nanotube length, and chirality. Thus, optimization of CNT structural elements may prove critical for electronic applications, including the development of field emission devices (FEDs).
FEDs are devices that capitalize on the cold emission of electrons. A typical field emission device includes at least a cathode, emitters, and an anode spaced from the cathode. A certain voltage applied between the cathode and the anode may cause electrons to be emitted from the emitters. The electrons travel in the direction from the cathode to the anode. These devices can be used in a variety of applications including, but not limited to, microwave vacuum tube devices, power amplifiers, ion guns, high energy accelerators, free electron lasers, and electron microscopes, and in particular, flat panel displays. Flat panel displays can be used as replacements for conventional cathode ray tubes. Thus, they have applications in television and computer monitors.